The socially-isolated mouse: a model to study the putative role of allopregnanolone and 5alpha-dihydroprogesterone in psychiatric disorders

Allopregnanolone (3alpha,5alpha-TH PROG) and 5alpha-dihydroprogesterone (5alpha-DH PROG), the two most important neuroactive steroids synthesized in the brain, potently modulate neuronal activity by allosterically regulating GABA action at GABA(A) receptors or by changing specific GABA(A) receptor subunit gene expression, respectively. We recently reported [Proc. Natl. Acad. Sci. USA 95 (1998) 3239] that in patients with severe depression there is a decrease in the CSF levels of 3alpha,5alpha-TH PROG, which is normalized by treatment with drugs (i.e. fluoxetine) that improve psychopathology. The mechanism by which fluoxetine and other selective serotonin reuptake inhibitors normalize 3alpha,5alpha-TH PROG CSF levels appears to involve a direct stimulation of 3alpha-hydroxysteroidoxidoreductase (3alpha-HSD), an enzyme that catalyses the reduction of 5alpha-DH PROG into 3alpha,5alpha-TH PROG. Here, we propose the use of socially-isolated mice that have a downregulation of 3alpha,5alpha-TH PROG and of 5alpha-DH PROG expression to establish a model to study the behavioral consequences of this deficiency. After 4-6 weeks of isolation, these mice exhibit increased anxiety and aggressive behavior and also a decreased response to the administration of GABA-mimetic drugs. In these mice, the decrease in 3alpha,5alpha-TH PROG is selectively normalized by the use of fluoxetine in doses that reduce behavioral abnormalities. In addition, the expression of 5alpha-reductase Type I mRNA and protein was lower in socially-isolated mice than that in group-housed mice whereas 3alpha-HSD mRNA expression remained unchanged. The results of these studies may enable us to design drugs that specifically affect neurosteroidogenic enzymatic activities and may provide an efficacious treatment for the psychopathologies associated with psychiatric disorders.

Brain 5alpha-dihydroprogesterone and allopregnanolone synthesis in a mouse model of protracted social isolation

Allopregnanolone (ALLO), is a brain endogenous neurosteroid that binds with high affinity to gamma-aminobutyric acid type A (GABA(A)) receptors and positively modulates the action of GABA at these receptors. Unlike ALLO, 5alpha-dihydroprogesterone (5alpha-DHP) binds with high affinity to intracellular progesterone receptors that regulate DNA transcription. To investigate the physiological roles of ALLO and 5alpha-DHP synthesized in brain, we have adopted a mouse model involving protracted social isolation. In the frontal cortex of mice, socially isolated for 6 weeks, both neurosteroids were decreased by approximately 50%. After administration of (17beta)-17-(bis-1-methyl amino carbonyl) androstane-3,5-diene-3-carboxylic acid (SKF105,111), an inhibitor of the enzyme (5alpha-reductase Type I and II) that converts progesterone into 5alpha-DHP, the ALLO and 5alpha-DHP content of frontal cortex of both group-housed and socially isolated mice decreased exponentially to 10%-20% of control values in about 30 min. The fractional rate constants (k h(-1)) of ALLO and 5alpha-DHP decline multiplied by the ALLO and 5alpha-DHP concentrations at any given steady-state estimate the rate of synthesis required to maintain that steady state. After 6 weeks of social isolation, ALLO and 5alpha-DHP biosynthesis rates were decreased to 30% of the values calculated in group-housed mice. Moreover, in socially isolated mice, the expression of 5alpha-reductase Type I mRNA and protein was approximately 50% lower than in group-housed mice whereas 3alpha-hydroxysteroid oxidoreductase mRNA expression was equal in the two groups. Protracted social isolation in mice may provide a model to investigate whether 5alpha-DHP by a genomic action, and ALLO by a nongenomic mechanism down-regulate the action of drugs acting as agonists, partial agonists, or positive allosteric modulators of the benzodiazepine recognition sites expressed by GABA(A) receptors.

A study of ginsenoside-Rd in a renal ischemia-reperfusion model

The effect of ginsenoside-Rd in ischemic-reperfused rats was examined. In control rats, blood and renal parameters and the activities of antioxidative enzymes in renal tissue deviated from the normal range, indicating dysfunction of the kidneys. In contrast, when ginsenoside-Rd was given orally for 30 consecutive days prior to ischemia and reperfusion, the activities of the antioxidation enzymes superoxide dismutase, catalase and glutathione peroxidase were higher, while malondialdehyde levels in serum and renal tissue were lower in the treated rats than in the controls. Decreased levels of urea nitrogen and creatinine in serum demonstrated a protective action against the renal dysfunction caused by ischemia and recirculation. On the other hand, it was demonstrated that ginsenoside-Rd affected cultured proximal tubule cells subjected to hypoxia-reoxygenation, probably by preventing oxygen free radicals from attacking the cell membranes.

Selegiline improves cardiac sympathetic terminal function and beta-adrenergic responsiveness in heart failure

Selegiline is a centrally acting sympatholytic agent with neuroprotective properties. It also has been shown to promote sympathetic reinnervation after sympathectomy. These actions of selegiline may be beneficial in heart failure that is characterized by increased sympathetic nervous activity and functional sympathetic denervation. Twenty-seven rabbits with rapid cardiac pacing (360 beats/min, 8 wk) and twenty-three rabbits without pacing were randomly assigned to receive selegiline (1 mg/day, 8 wk) or placebo. Rapid pacing increased plasma norepinephrine (NE) and decreased left ventricular fractional shortening, baroreflex sensitivity, cardiac sympathetic nerve terminal profiles, cardiac NE uptake activity, and myocardial beta-adrenoceptor density. Selegiline administration to animals with rapid ventricular pacing attenuated the increase in plasma NE and decreases in fractional shortening, baroreflex sensitivity, sympathetic nerve profiles, NE uptake activity and beta-adrenoceptor density. Thus selegiline appears to exert a sympatholytic and cardiac neuroprotective effect in pacing-induced cardiomyopathy. The effects are potentially beneficial because selegiline not only improves cardiac function but also increases baroreflex sensitivity in heart failure.

Alterations by norepinephrine of cardiac sympathetic nerve terminal function and myocardial beta-adrenergic receptor sensitivity in the ferret: normalization by antioxidant vitamins

BACKGROUND

Chronic excessive norepinephrine (NE) causes cardiac sympathetic nerve terminal abnormalities, myocardial beta-adrenergic receptor downregulation, and beta-adrenergic subsensitivity. The present study was carried out to determine whether these changes could be prevented by antioxidants.

METHODS AND RESULTS

Ferrets were administered either NE (1.33 mg/d) or vehicle by use of subcutaneous pellets for 4 weeks. Animals were simultaneously assigned to receive either antioxidant vitamins (beta-carotene, ascorbic acid, and alpha-tocopherol) or placebo pellets. NE increased plasma NE 4- to 5-fold but had no effect on heart rate, heart weight, arterial pressure, or left ventricular systolic function. However, myocardial NE uptake activity and NE uptake-1 site density were reduced, as well as cardiac neuronal NE, tyrosine hydroxylase, and neuropeptide Y. In addition, there was a decrease in myocardial beta-adrenergic receptor density with a selective decrease of the beta(1)-receptor subtype, reduction of the high-affinity site for isoproterenol, decreased basal adenylyl cyclase activity, and the adenylyl cyclase responses to isoproterenol, Gpp(NH)p, and forskolin. All of these changes were prevented by antioxidant vitamins. The effects of NE on myocardial beta-adrenergic receptor density, NE uptake-1 carrier site density, and neuronal NE were also prevented by superoxide dismutase or Trolox C.

CONCLUSIONS

The toxic effects of NE on the sympathetic nerve terminals are mediated via the formation of NE-derived oxygen free radicals. Preservation of the neuronal NE reuptake mechanism is functionally important, because the antioxidants also prevented myocardial beta-adrenergic receptor downregulation and postreceptor abnormalities. Thus, antioxidant therapy may be beneficial in heart failure, in which cardiac NE release is increased.

Protection of the kidney by Wen-Pi-Tang against ischemia-reperfusion injury

Electrophoretic and densitometric data revealed induction of apoptosis in the kidney due to experimentally induced ischemia-reperfusion injury. Such apoptosis in the kidney was reduced in rats given 62.5 or 125 mg/kg body wt./day Wen-Pi-Tang orally for 30 days prior to ischemia-reperfusion. An increase in the dose of Wen-Pi-Tang was associated with suppressed fragmentation of DNA, a ladder pattern of low-molecular-weight molecules, resulting in a beneficial effect on renal function.

Alterations in cardiac adrenergic terminal function and beta-adrenoceptor density in pacing-induced heart failure

Congestive heart failure is associated with cardiac adrenergic nerve terminal changes and beta-adrenoceptor density downregulation. To study the temporal sequence of these changes, we performed studies in rabbits at 2, 4, and 8 wk of cardiac pacing (360 beats/min) and at 1, 2, and 4 wk after cessation of pacing. Rapid pacing produced left ventricular (LV) dysfunction and an increase in plasma norepinephrine (NE) in 1-2 wk. At week 2, NE uptake activity, NE uptake-1 density, and adenylyl cyclase responses to isoproterenol, 5'-guanylyl imidodiphosphate [Gpp(NH)p], and forskolin reduced. However, immunostained tyrosine hydroxylase profile, beta-adrenoceptor density, and NE histofluorescence did not reduce until 4-8 wk of pacing. After cessation of cardiac pacing, LV function normalized quickly, followed by return of tyrosine hydroxylase and NE profiles in 1 wk and adenylyl cyclase responses to agonists and NE uptake activity in 2 wk. Myocardial beta-adrenoceptor density returned to normal by 4 wk after cessation of pacing. Our results suggest that there is no permanent structural neuronal damage in the myocardium within the first 8 wk of rapid cardiac pacing. Abnormal myocardial NE reuptake mechanism may play an important pathophysiological role in heart failure.

Involvement of peripheral type of benzodiazepine receptor in social isolation stress-induced decrease in pentobarbital sleep in mice

Our previous studies have shown that central-type benzodiazepine (BZD) receptors (CBR) and neurosteroids capable of modulating GABA(A) receptor function are involved in the decrease of pentobarbital (PB)-induced sleep caused by social isolation stress in mice. In this study, to further clarify the mechanism underlying this decrease, we investigated the possible involvement of peripheral-type BZD receptors (PBR) which play an important role in neurosteroidogenesis in PB sleep in socially isolated mice. Socially isolated mice showed significantly shorter duration of PB-induced sleep than group-housed animals. When injected intracerebroventricularly (i.c.v.), FGIN-1-27 (FGIN, 25-100 nmol), a selective PBR agonist, and PK11195 (PK, 14-28 nmol), a PBR antagonist, and pregnenolone (PREG, 15-30 nmol), a neurosteroid precursor, dose-dependently normalized the PB sleep in isolated mice without having an effect on the group-housed animals. In contrast, pregnenolone sulfate (PS, 24 nmol), an endogenous neurosteroidal negative allosteric modulator of the GABA(A) receptor, reduced PB sleep in group-housed but not isolated mice. PS, at the same dose, significantly attenuated the effects of FGIN (100 nmol), PK (28 nmol) and PREG (30 nmol) in isolated mice, while FGIN (100 nmol), PK (28 nmol) and pregnenolone (30 nmol) significantly blocked the effect of PS (24 nmol) in group-housed mice. These results suggest that the PBR-mediated decrease in the genesis of neurosteroid(s) possessing a GABA(A) receptor agonistic profile is also partly involved in the down regulation of the GABA(A) receptor following long-term social isolation and contributes to the decrease of PB-induced sleep in isolation stressed mice.

Myocardial beta-adrenoceptor down-regulation by norepinephrine is linked to reduced norepinephrine uptake activity

Chronic administration of norepinephrine for 8 weeks has been shown to reduce neuronal norepinephrine uptake activity and increase interstitial norepinephrine concentration in the heart. To determine whether the changes could lead to myocardial beta-adrenoceptor down-regulation or beta-adrenergic subsensitivity, we measured left ventricular contractile responses to dobutamine, myocardial beta-adrenoceptor density, beta subtype distribution, competitive inhibition agonist binding, and adenylyl cyclase activity activation by isoproterenol, 5'-guanylylimidodiphosphate, and forskolin in dogs after a norepinephrine or saline infusion for 8 weeks. We found that norepinephrine infusion reduced myocardial beta-adrenoceptor density, beta(1)-adrenoceptor subtype density, and high-affinity site for isoproterenol. Left ventricular contractile responses to dobutamine were reduced in the norepinephrine-infused animals. In addition, norepinephrine infusion decreased the basal adenylyl cyclase activity and the adenylyl cyclase responses to isoproterenol, 5'-guanylylimidodiphosphate, and forskolin. The findings indicate that a decrease in cardiac norepinephrine uptake predisposes the heart to norepinephrine-induced myocardial beta-adrenoceptor down-regulation, and that norepinephrine, when present in a sufficient amount over a long period as it is in chronic heart failure, can reduce myocardial beta-adrenergic responsiveness by both homologous and heterologous desensitization.

ACE inhibition improves cardiac NE uptake and attenuates sympathetic nerve terminal abnormalities in heart failure

Cardiac sympathetic nerve terminal dysfunction plays an important role in the downregulation of myocardial beta-adrenoceptors in heart failure. To determine whether chronic angiotensin-converting enzyme (ACE) inhibition improved cardiac sympathetic nerve terminal function and hence increased myocardial beta-adrenergic responsiveness, we administered ACE inhibitors to dogs with chronic right-sided heart failure (RHF) produced by tricuspid avulsion and pulmonary artery constriction. The RHF animals exhibited fluid retention, elevated right heart filling pressures, blunted inotropic response to isoproterenol, and reduced beta-adrenoceptor density. These changes were accompanied by decreases in right ventricular norepinephrine (NE) uptake and neuronal NE histofluorescence and tyrosine hydroxylase immunoreactive profiles. ACE inhibitors had no effect on the production of heart failure but greatly reduced the attenuation of cardiac NE uptake, neuronal NE histofluorescence, and tyrosine hydroxylase immunoreactive profiles. ACE inhibition also improved the inotropic response to isoproterenol and restored myocardial beta-adrenoceptor density. The changes probably are caused by reduction of cardiac NE release by ACE inhibition and may contribute to the beneficial effects of ACE inhibitor therapy in patients with chronic heart failure.

Involvement of diazepam binding inhibitor and its fragment octadecaneuropeptide in social isolation stress-induced decrease in pentobarbital sleep in mice

Diazepam binding inhibitor (DBI) and its fragment, octadecaneuropeptide (ODN), are putative endogenous ligands for benzodiazepine (BZD) receptors and have been shown to act as an inverse BZD receptor agonist in the brain. A previous study suggested that the social isolation stress-induced decrease in pentobarbital sleep in mice was partly due to endogenous substances with an inverse BZD receptor agonist-like property. In this study, we examined the effects of DBI and ODN on pentobarbital sleep in group-housed and socially isolated mice to test the possible involvement of DBI and ODN in a social isolation-induced decrease in pentobarbital sleep. The socially isolated mice showed significantly shorter durations of pentobarbital (50 mg/kg, intraperitoneally, i. p.) sleep compared to the group-housed animals. When injected intracerebroventricularly (i.c.v.), DBI and ODN (3 and 10 nmol) dose-dependently shortened the pentobarbital-induced sleeping time in group-housed mice at the same dose range, but these peptides had no effect on the sleeping time in socially isolated animals. In contrast, flumazenil (16.5-33 nmol, i.c.v.), a BZD receptor antagonist, reversed the pentobarbital sleeping time in socially isolated mice to the level of group-housed animals without affecting the sleeping time in group-housed animals. The effects of DBI and ODN in group-housed mice were significantly blocked by flumazenil (33 nmol, i.c.v.). Moreover, the effect of flumazenil in socially isolated mice was significantly attenuated by DBI and ODN (10 nmol, i.c.v.). These results suggest that the changes in the activity of DBI and/or ODN are partly involved in the social isolation-induced decrease in the hypnotic action of pentobarbital in mice.

Diazepam binding inhibitor (DBI) gene expression in the brains of socially isolated and group-housed mice

Diazepam binding inhibitor (DBI), a putative endogenous polypeptide ligand for benzodiazepine (BZD) receptors, has been shown to act as an inverse BZD receptor agonist in the brain. We previously suggested that the social isolation stress-induced decrease in pentobarbital sleeping time in mice was partly due to an increase in the activity of endogenous substances with an inverse BZD receptor agonist-like property such as DBI. In this study, we examined whether the DBI gene expression is affected by socially isolated stress. Consistent with the previous findings, the in situ hybridization result showed very strong signals of DBI mRNA around the regions of the third ventricle, especially the lining cells, the arcuate nucleus of the hypothalamus and the cerebellum, in both socially isolated and group-housed animals. Unexpectedly, however, semi-quantitative experiments with reverse transcription polymerase chain reaction technique revealed that socially isolated mice had significantly less expression of DBI mRNA in the hypothalamus than group-housed animals, and no difference in the expression in the other brain areas was observed between two animal groups. We discuss the relationship between the decrease of DBI mRNA expression in the hypothalamus and the decrease of GABA(A) receptor function following long-term social isolation in mice.

Protective effects of some flavonoids on the renal cellular membrane

By assaying lactate dehydrogenase and malondialdehyde leakage from LLC-PK1 cells in culture, a study was conducted to clarify whether flavonoid compounds ameliorate renal cellular injury. The cells were cultured with various concentrations of samples under routine conditions. The results demonstrated that baicalin, cirsimaritin, 6-hydroxyluteolin, luteolin, plantaginin, rhoifolin, sorbarin, afzelin, hyperin, isoquercitrin, isorhamnetin, kaempferitrin, kaempferol-7-glucoside, oxyayanin A, quercetin, quercitrin, rhamnetin and rutin exerted marked protective effects on the cells, whereas acacetin, apigenin, apiin, cirsilineol, genkwanin, pectolinarin and tetramethylquercitin had virtually no effect. In the light of these findings, we propose that the general capability of these compounds is largely decided by the number and position of phenolic hydroxyl groups linked to the structural backbone.

Overexpression of nerve growth factor in the heart alters ion channel activity and beta-adrenergic signalling in an adult transgenic mouse

1. The electrophysiological and pharmacological properties of cardiac myocytes from the hearts of adult transgenic mice engineered to overexpress nerve growth factor (NGF) in the heart were studied. 2. There was a 12% increase in the ventricular myocyte capacitance in NGF myocytes consistent with cardiac hypertrophy, and action potential duration at 90% repolarization (APD90) was prolonged by 142 % compared with wild-type (WT) myocytes. This was due, at least in part, to a decrease in the density of two K+ currents, Ito and IK(ur), which were significantly reduced in NGF mice with no change in their electrophysiological characteristics. We found no change in the current density or electrophysiological properties of the L-type Ca2+ current. 3. The effect on Ito and IK(ur) of TEA and 4-aminopyridine (4-AP) was not different in cells isolated from WT and NGF mice. The prolongation of APD observed in NGF cells was mimicked in WT cells by exposure to 1 mM 4-AP, which partially blocked Ito, completely blocked IK(ur) and increased APD90 by 157%. 4. The isoprenaline-induced increase in ICa was significantly smaller in NGF myocytes than in WT myocytes. This was not due to a decrease in beta-adrenergic receptor (beta-AR) density, as this was increased in NGF tissue by 55%. Analysis of beta-AR subtypes showed that this increase was entirely due to an increase in beta2-AR density with no change in beta1-ARs. 5. The response of the beta-AR-coupled adenylyl cyclase system to isoprenaline, Gpp(NH)p and forskolin was studied by measuring cAMP production. In NGF tissue, isoprenaline elicited a significantly smaller response than in WT myoyctes and this was not due to reduced adenylyl cyclase activity as the responses of NGF tissue to guanylylimidodiphosphate (Gpp(NH)p) and forskolin were unaffected. 6. In conclusion, the overexpression of NGF in the mouse heart resulted in a decrease in the current density of two K+ channels, which contributed to the prolongation of the cardiac action potential. Despite an increase in beta2-AR density in the hearts of the NGF mice, the response to isoprenaline was diminished, and this was due to an uncoupling of the beta-ARs from the intracellular signalling cascade. These potentially pathological changes may be involved in the occurrence of ventricular arrhythmias in cardiac hypertrophy and failure, and this mouse provides a novel model in which to study such changes.

Study on the inhibitory effect of tannins and flavonoids against the 1,1-diphenyl-2 picrylhydrazyl radical

Fifty-one tannins and forty-one flavonoids isolated from Oriental medicinal herbs were evaluated for their antioxidant ability with a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-generating system. The results showed that tannins and certain flavonoids are potential free-radical scavengers, and that their activity against the DPPH radical is closely associated with their chemical structure. A comparison of the two classes of compounds showed that tannins have more potential than flavonoids because almost all the tannins demonstrated significant scavenging action within a low concentration range, whereas the activity of flavonoids varied distinctively among the different compounds. An increase of galloyl groups, molecular weight, and ortho-hydroxyl structure enhanced the activity of tannins, whereas the number and position of hydroxyl groups were important features for the scavenging of free radicals by flavonoids. Moreover, it appeared that when the free hydroxyl group was methoxylated or glycosylated, the inhibitory activity was obviously decreased or even abolished.

Effects of Japanese black tea on atherosclerotic disorders

The atherogenic index was found to be significantly better in rats fed a high-cholesterol diet supplemented with black tea extract than in the ones not given the extract. It was also evident that black tea inhibited the proliferation of smooth muscle cells involved in the development and progression of atherosclerosis, and suppressed the production of oxidized low-density lipoprotein, a cause of lipid accumulation. It thus seems likely that black tea has an antiatherosclerotic action.

Magnesium lithospermate B ameliorates cephaloridine-induced renal injury

To determine whether magnesium lithospermate B ameliorates renal injury induced by cephaloridine, the effect of cephaloridine was investigated in rats given magnesium lithospermate B for 20 days preceding cephaloridine administration and in control rats given no magnesium lithospermate B. In the control rats, blood and urinary parameters and the activity of radical-eliminating enzymes in the renal tissue deviated from the normal range, indicating damage to the kidneys. In contrast, rats given magnesium lithospermate B showed decreased urine volume, increased urinary osmotic pressure, and decreased urinary levels of glucose, protein, sodium and potassium, denoting less damage to the kidney. In this group, the urinary nitrite/nitrate ratio, and the activities of superoxide dismutase and catalase in the renal tissue were increased, while the malondialdehyde levels were decreased, suggesting the involvement of radicals in the normalizing of kidney function. The increased levels of urea nitrogen in the blood of rats with induced renal failure were also lowered by administering magnesium lithospermate B.

Magnesium lithospermate B ameliorates cisplatin-induced injury in cultured renal epithelial cells

A study was conducted to clarify whether magnesium lithospermate B ameliorates cisplatin-induced renal injury in terms of lactate dehydrogenase and malondialdehyde leakage from LLC-PK1 cells in culture. Magnesium lithospermate B was shown to suppress the cytotoxicity of cisplatin, the suppressive effect increasing with the dose of magnesium lithospermate B.

Influence of green tea and its three major components upon low-density lipoprotein oxidation

The abilities of green tea extract and its three major components to inhibit lipid peroxidation in low-density lipoprotein (LDL) catalyzed by copper were tested in vitro using malondialdehyde as a parameter of antioxidant activity. The results demonstrated that green tea extract markedly delays peroxidation with a dose-dependent pattern. Of the three components, polyphenols had the strongest action. Similar action was also shown in the theanine-treated group but was weaker than in the former, whereas caffeine had a very limited effect. Based on these data, it is concluded that green tea extract can effectively inhibit peroxidation and that this activity is due largely to the polyphenols it contains. According to the ultraviolet spectra, copper chelation is suggested to be one of the possible mechanisms of LDL antiperoxidation.

Proof that green tea tannin suppresses the increase in the blood methylguanidine level associated with renal failure

The effects of a green tea tannin mixture and its individual tannin components on methylguanidine were examined in rats with renal failure. The green tea tannin mixture caused a dose-dependent decrease in methylguanidine, a substance which accumulates in the blood with the progression of renal failure. Among individual tannin components, the effect was most conspicuous with (-)-epigallocatechin 3-O-gallate and (-)-epicatechin 3-O-gallate, while other components not linked to gallic acid showed only weak effects. Thus, the effect on methylguanidine was found to vary among different types of tannin.

Magnesium lithospermate B suppresses the increase of active oxygen in rats after subtotal nephrectomy

Subtotally nephrectomized rats were found to have decreased activities of superoxide dismutase (SOD) and catalase, and spin trapping with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) showed that the amount of hydroxyl radical in the residual kidney tissue was greater than that in normal rat kidney. This indicated both direct and indirect involvement of free radicals in renal failure. In contrast, rats given magnesium lithospermate B (10 mg/kg body weight) orally for 30 days after subtotal nephrectomy showed restoration of SOD and catalase activities to almost normal levels. Hydroxyl radical, which is highly reactive and for which there is no scavenger system in the body, was decreased markedly in kidney homogenates obtained from rats given magnesium lithospermate B and in an experimental system for hydroxyl radical production to which magnesium lithospermate B was directly added. The increased levels of uremic toxins in the blood were also low in rats given magnesium lithospermate B. This indicates that magnesium lithospermate B helps to inhibit the progression of renal failure by scavenging radicals.

Inhibitory effect of green tea on injury to a cultured renal epithelial cell line, LLC-PK1

When cells from a cultured renal epithelial cell line, LLC-PK1, were cultured under hypoxic conditions (oxygen concentration of 2% or less) before reoxygenation was applied (95% air, 5% CO2), the leakage of lactate dehydrogenase (LDH) into the medium increased. This phenomenon was inhibited in the presence of dimethyl sulfoxide, a hydroxyl radical scavenger, suggesting the involvement of free radicals. Such oxidative stress was significantly inhibited by a green tea extract, and more potently by a tannin mixture. On the other hand, under ordinary culture conditions (95%, air, 5% CO2), there was cell injury, although the LDH leakage was less than that under hypoxia/reoxygenation, and such injury was inhibited by the green tea extract and the tannin mixture.

Alterations of alpha1-adrenoceptor subtypes in the hearts of thyroxine-treated rats

Alterations in the cardiac alpha1-adrenoceptor and its subtypes in thyroxine-treated rats were studied by means of radioligand binding assays, measurement of contractile response and reverse transcription-polymerase chain reaction (RT-PCR). The results showed that in thyroxine-treated rats the cardiac alpha1-adrenoceptor density (Bmax) was reduced from 51.6 +/- 6.0 fmol/mg in control to 40.9 +/- 3.7 fmol/mg (P<0.01); and the percentage of high affinity sites for 5-methyl-urapidil decreased from 23.3 +/- 2.0% in control to 10.8 +/- 2.0% in thyroxine-treated rats (P<0.05). The data indicated that the high-affinity sites for 5-methyl-urapidil (alpha1A-adrenoceptor) were reduced (from 12.0 to 4.4 fmol/mg), but the low-affinity sites for 5-methyl-urapidil (alpha1B- plus alpha1D-adrenoceptor) were not changed (from 39.6 to 36.5 fmol/mg). RT-PCR showed that steady-state levels of mRNA for alpha1A- and alpha1B-adrenoceptors were decreased, while that for alpha1D-adrenoceptor was raised in thyroxine-treated rats. In the isolated electrically driven left atria the phenylephrine-induced maximal contractions were reduced from 258 +/- 17 mg in control to 188 +/- 24 mg in thyroxine-treated rats (P<0.05). The pA2 values of 5-methyl-urapidil were reduced from 8.89 +/- 0.36 in control to the hyperthyroidism of 7.87 +/- 0.43 in thyroxine-treated rats (P<0.05). Chlorethylclonidine preincubation shifted concentration-response curves for phenylephrine to the right and reduced the maximal response to a lesser extent in thyroxine-treated rats than in control rats. Thus we concluded that the total number of cardiac alpha1-adrenoceptors is reduced in thyroxine-treated rats. The change is subtype selective, with alpha1A- and alpha1B-adrenoceptors being reduced in number and alpha1D-adrenoceptor being increased.